A safety razor generally has a handle and a blade unit carried on the handle and at least one blade with a sharp cutting edge. In the course of shaving the blade unit is applied against the skin and the blade or blades are moved across the skin so that the sharp cutting edges engage and cut through the hairs protruding from the skin. The blade unit can be fixed on the handle with the intention that the entire razor should be discarded when the cutting edges have become dull and no longer capable of providing a comfortable shave. Alternatively the blade unit may be removably mounted on the handle so that the blade unit can be replaced by a new blade unit when the sharpness of the blades has diminished to an unacceptable level. Replaceable blade units are often referred to as shaving cartridges.
Some razors may include an electrically driven vibration mechanism for vibrating the razor, since vibrating may have a beneficial effect on razor performance. A simple and convenient vibration generating mechanism has of an electric motor with a weight mounted eccentrically on its output shaft. The vibration mechanism may incorporate a piezoelectric device for producing the vibrations. The vibration mechanism and a battery for providing electric power to the motor can be conveniently housed in the razor handle. Some safety razors include a light emitting diode which is illuminated when the safety razor is turned on. Some vibrating razors include a power meter or indication to indicate the battery power remaining and/or to indicate when a new battery is needed.
A vibration mechanism may be adapted to vibrate only one or more selected components of the blade unit, such as the guard which contacts the skin in front of the blades, or one or more blades, and the vibration may be directional, for instance directed lengthwise of the blades to encourage a slicing cutting action or transverse to the blades. Another possibility is for an element to be vibrated in a direction generally perpendicular to the skin surface being shaved.
Other forms of electrical devices besides vibration generators may be included in wet razors, some examples of such devices being:
(i) heating devices for heating one or more blades or other components of a blade unit which contact the skin during shaving, such as Peltier devices or electrical resistance or ohmic heating devices;
(ii) dispensing devices for delivering a shaving enhancement product to the skin and which may be activated by operation of a motor driven pump or by operation of a valve having an electrically controlled actuator, shaving enhancement products which can be delivered at a safety razor blade unit during performance of a shaving stroke including those with the qualities and properties mentioned in patent application No. WO00/47374 the contents of which are incorporated herein by reference;
(iii) conditioning devices to prepare the skin and/or hairs ready to be cut by the blades, such as a roller mounted in the region of the guard of the blade unit and adapted to be rotated about its axis for encouraging hairs lying against the skin to stand up for cutting;
(iv) illumination devices for illuminating an area of skin being shaved; and
(v) actuators for adjusting the blade unit in accordance with prevailing shaving conditions detected by a sensor.
When there is an electrical device included in a safety razor it is often convenient for the device to be operated by a replaceable or rechargeable electric storage battery which can be housed within the razor handle. To conserve battery power, the electrical device may be disconnected from the battery during periods when the razor is not in use. In some cases it may be immediately obvious to a user when connection between the electrical device and battery established, such as if the device is a vibration generator which is set into operation as soon as the electrical connection to the battery is made, but there may be other cases where it is not so obvious.
Some razors have a blade unit including an electrically conductive (e.g., metal) casing that serves as an electrode for electrical contact with the hand of a user. The handle may also serve as an electrode for electrical contact with the user's skin. A control device starts a vibration source when a person holding the razor by the handle touches the blade unit against the skin surface, such as when shaving. After the blade unit is lifted away from the skin surface, the control device stops the vibration source.
A capacitive sensor detects the proximity of a conductive object. Capacitive sensing is used in interface applications to build non-contact switches (or sensors). Very simply, a capacitive sensor is a pair of adjacent plates. When a conductive object is placed in proximity to these plates, there is capacitance between the electrodes and the conductive object. The capacitance measured by the sensor is a function of the distance from the sensor to the object. The most common form of capacitance sensor array is a set of capacitors where one side of each is grounded. The presence of a conductive object increases the capacitance of the switch to ground, and determining sensor activation is only a matter of measuring change in capacitance.
A capacitive sensor often requires a number of other support functions for practical use, such as programmable current source, an analog multiplexer, and an auto-calibration system, for example. Sensor support may be implemented with a mixed-signal programmable system-on-chip device.